Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
#define int_inf 1000000000 //1e9
#define ll_inf  1000000000000000000 //1e18

using namespace std;

void find(int x, int y);


int h, w;
char s[60][60];
int map_[50][50];
int dx[]={0, 1, 0, -1};
int dy[]={-1, 0, 1, 0};
int main(){
	cin >> h >> w;
	for(int i=0; i<h; i++){
	for(int j=0; j<w; j++){
		cin >> s[i][j];
		map_[i][j]=int_inf;
	}}
	map_[0][0]=1;
	find(0, 0);
	int white=0; int cost=map_[h-1][w-1];
	for(int i=0; i<h; i++){
	for(int j=0; j<w; j++){
		if(s[i][j]=='.') white+=1;
	}}
	
	if(cost==int_inf){ cout<<-1<<endl; return 0; }
	else{ cout<<white-cost<<endl; return 0; }
	return 0;
}

void find(int x, int y){
	int nx, ny;
	for(int i=0; i<4; i++){
		nx=x+dx[i]; ny=y+dy[i];
		if(nx>=0 && nx<h && ny>=0  && ny<w){
			if(s[nx][ny]=='.' && map_[nx][ny] > map_[x][y]+1){
				map_[nx][ny] = map_[x][y]+1;
				find(nx, ny);
			}
		}
	}
}